Re: Audio problem in my ubitx

Bill Cromwell <wrcromwell@...>

Hi Jerry,

One of your questions was already answered and you even requoted it. He said there is no audio in the speaker nor in the earphones. It could still be wired wrong.

In my V3 with CEC software there is a setting in the setup menu to disable the transmit. I thought I would use that to play with the sidetone and use the uBitx as a $150 code practice oscillator. There was very little sidetone, extremely faint. I don't know if his software has a feature to disable the transmitter. He may also not have wired the brown wire to the power supply so there is no drain voltage applied to the finals. No transmit output.

And what about that resistor to the key jack? That produces at least some of the symptoms. Other hams have decided they don't use CW and don't need that resistor. WRONG! There new rigs worked right AFTER they installed that.

I hope all of this helps him make progress toward a working radio.


Bill KU8H

On 1/20/19 9:44 AM, Jerry Gaffke via Groups.Io wrote:
No receiver audio, sounds like it could be a wiring error around either
the volume control or the output of the audio amp to the speaker.
Triple check that wiring.  What kind of speaker or headphones are you using?
First, lets make sure it is receiving.
Verify that RX has 12 volts (measured to ground) for receive (measure either end of either R18 or R38,
near the top of the schematic) and that TX is low (measure either end of R28 or R40,
which are below R18 and R38).
If TX is 12v and RX is 0v, then it is trying to transmit, perhaps a problem with how
the PTT switch or the key got wired up.
Maybe wire the SPK output directly from the uBitx to an 8 ohm speaker, and then to board ground,
this will go around any wring errors at the speaker/headphone jack.
Then remove the volume pot, wire directly from M1 to VOL-M to go around the relay
between M1 and M2, the volume control  (and the AGC circuit at Q74 if this is a v4 uBitx).
Power up, the sound through the speaker will be very very loud if it now works.
Touch the end of one meter of wire (we are using it as an antenna to pick up local radio noise)
to the test point TP20 (on the right side of the v4 schematic, between modulator and audio pre-amp).
This will make a pop in the speaker if the audio amps are working.
If none of that gets the audio amplifier going, you might try replacing the final stage between VOL-M and SPK
with a small LM386 amplifier such as this:
You also seem to have a problem with the transmitter.
Let's get the receiver working first.
It will help if you tell us exactly what you have.
What version of the uBitx, v3 or v4?
Speaker or headphones?
Power supply?
Any mistakes you might have made already that could have damaged the radio,
such as reversing the power supply leads or a power supply more than 13 volts?
Did you power it up with the Raduino connector not quite lined up correctly?
Does the raduino power up, can you select a frequency in the display by turning the encoder knob?
Perhaps a picture or two showing us how you wired it up?
On Sat, Jan 19, 2019 at 09:00 PM, Avijit wrote:
I have assembled my Ubitx yesterday but I am not getting any audio.
Here are the details :
1. No audio coming out on speaker as well as headphones.
2. When I am turning the volume control to the full only a
screeching sound is emanating.
3. Tried with another volume pot but no difference.
4. When i am connecting the cw key occasional cw tone is heard very
faintly but nothing happens with pressing the key.
5. No rf power is visible on the meter when key is pressed.
Please help.
Thanks and regards
bark less - wag more

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